prevent excessive ring fragmentation due to repeated space requests #2184
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Merging a ring now indicates whether the ring has been updated. This prevents excessive allocation retries, which in turn can result in repeated space requests - i.e. if an allocation cannot proceed due to lack of space - which in turn can result in excessive ring fragmentation since many of the requests will result in the creation of a new ring entries, due to the need to split ranges. Fixes #2181.
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I suggest reviewing the individual commits of this PR rather than the whole diff, since the refactoring makes it look far bigger than it actually is. |
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There can be many reasons why the ring is updated which do not behoove a repeated request for space. Would it not be better to have the code know when a request is in flight, and not to repeat that request unless we suspect the target is not going to respond? |
That is not easy to work out and will necessarily introduce another timeout or similar constant. I know that this PR does not eliminate repeated space requests. I said that much in #2181 ("the problem could probably be reduced significantly"). |
| // entries belonging to ourPeer. Returns the merged entries and an | ||
| // indication whether the merge resulted in any changes, i.e. the | ||
| // result differs from the original. | ||
| func (es entries) merge(other entries, ourPeer mesh.PeerName) (entries, bool, error) { |
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Fixes #2181.